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The content of arachis oil in the mixture may also be deduced approximately
from the temperature at which the first crystals form :
Temperature       of
initial     precipi-
tation       .         .    35-38 31-33 28-30 25-26 22-24 20-22 18-20 16-17
Proportion of ara-
chis oil    .         .    100%     60%     50%     40%     30%     20%     10%     5%

The proportion of arachis oil in a mixture may, however, be determined
more exactly from the quantitative determination of the arachidic and lig-
noceric acids, the content in the pure oil being 4-80%. In this way as little
as 5% of arachis oil in admixture with other oils may be detected.

2. BELLIER'S METHOD (modified).1 Into a conical flask of about 100
c.c. capacity are pipetted I c.c. of the oil and 5 c.c. of about 8% alcoholic
caustic potash solution (80 grams of pure potassium hydroxide dissolved
in 80 c.c. of water and made up to I litre -with 90% alcohol). The flask is
closed with a stopper carrying a tube 80 cm. long (to avoid loss of alcohol)
and heated on a boiling water-bath with continual shaking until saponifi-
cation is complete (4-5 minutes). The liquid is then cooled to about 25
and shaken with 1-5 c.c. (exactly) of dilute acetic acid (i vol. of glacial
acetic acid + 2 vols. of water), 3 drops (not more) of glacial acetic acid
and 50 c.c. of 70% alcohol. If the liquid becomes turbid (as usually happens
if arachis oil is present in marked quantity), it is gently heated until clear,
the flask being then closed with a stopper through which passes a ther-
mometer with its bulb in the liquid. The flask is then cooled and shaken
in a water-bath so that the temperature of the liquid becomes exactly 16,
at which it is maintained for 5 minutes with gentle shaking.

If the liquid remains clear it is kept at 15-5 for 5 minutes, and if it still
remains clear, arachis oil is either absent or present in less proportion than
5%. The appearance of turbidity at 15-5 indicates the presence of arachis
oil (about 5%) in the oil. With higher proportions, marked turbidity
occurs even at 16. With pure arachis oil, the liquid begins to show
turbidity at about 40.

The temperature at which the alcoholic solution of the fatty acids, obtained
as described above, first becomes turbid serves to indicate approximately the
proportion of arachis oil in its mixtures with olive oil:

Temperature at which

turbidity appears.
Pure olive oil        .......    ii-5-i4'5

-|-   5% arachis oil  .        .        .               16-17
,,,.          10              ,,....       19-20

MM        20                                              25-26

MM           30                M                                             29-30

MM           40               ,,....       31-32

MM         50             M                                    33-34

,,M            60                                                                  35-36

MM           70                ,.....       36-37

MM           80                                                           38

MM           90                M                                             39

Pure arachis oil    .         .        .        .                        .40

1 The modifications of Belller's original method (Ann. de Chim. analyt., 1899, 4)
are due principally to Mansfeld (Z. Unt. Nahr. Genussm., 1905, XVII, p. 57). Adler
(ibid., 1912, XXIII, p. 676), Luers (##, 1912, XXIV, p, 683), an4 Evers (Analyst,
1912, p. 487),                                                                               25	3-66